Enhanced mid-infrared emissions of Ho3+/Er3+ co-doped Na5Y9F32 single crystal by introduction of Pr3+ ions

The Na5Y9F32 fluoride single crystals tri-doped with similar to 1 mol% Ho3+/similar to 1 mol% Er3+, and various concentrations of Pr3+ (0, 0.5, 0.8 and 1.0 mol%) were successfully grown by a modified Bridgman method. The absorption, Raman, emission spectra and fluorescence decay curves of Pr3+/Ho3+/Er3+ tri-doped Na5Y9F32 single crystals were studied systematically. The intensity parameters (Omega(2) = 1.96 x 10(-20) cm(2), Omega(4) = 1.66 x 10(-20) cm(2), Omega(6) = 1.46 x 10(-20) cm(2)) of Er3+ ions and emission cross-sections at similar to 2.7 mu m (1.76 x 10(-20) cm(2)) and similar to 2.9 mu m (1.34 x 10(-20) cm(2)) were calculated according to the measured absorption spectra. The emission intensities at similar to 2.7 mu m of Er3+: I-4(11/2) -> I-4(13/2) and similar to 2.9 mu m of Ho3+: I-5(6) -> I-5(7) were enhanced gradually as increase of Pr3+ concentrations from 0 to 1.0 mol% under excitation of 800 nm laser diode (LD). However, the similar to 2.0 mu m of Ho3+: I-5(7) -> I-5(8) and similar to 1.5 mu m of Er3+: I-4(13/2) -> I-4(15/2) were gradually reduced. The introduction of Pr3+ can greatly reduce the lifetimes of Er3+: I-4(13/2) and Ho3+: I-5(7) The energy transfer from Er3+: I-4(13/2) to Ho3+ : I-5(7) level and depopulating Er3+: I-4(13/2) and Ho3+: I-5(7) levels under the action of Pr3+ ions are responsible for the enhancement of similar to 2.7 and similar to 2.9 mu m emissions. The Pr3+/Ho3+/Er3+ tri-doped Na5Y9F32 single crystal may become a new choice for similar to 3.0 mu m mid-infrared solid-state laser. (C) 2020 Elsevier B.V. All rights reserved.